Orthogonal frequency division multiple access (OFDMA) communications use an orthogonal frequency-division multiplexing (OFDM) digital modulation scheme to deliver information across broadband networks. OFDMA is particularly suitable for delivering information across wireless networks.
The OFDM digital modulation scheme uses a large number of closely-spaced orthogonal subcarriers to carry information. Each subcarrier is capable of carrying a data stream across a network between OFDMA terminals.
OFDMA-based communication systems are well known to have high peak-to-average power (PAPR) ratios. A high PAPR may reduce transmitter power amplifier (PA) power efficiency by increasing PA back off, which may reduce the uplink link budget. Therefore, it is desirable to control the PAPR for uplink transmission.
Tone reservation (TR) techniques provide one method of controlling PAPR in uplink transmissions. TR techniques reserve a set of subcarriers for PAPR reduction. The reserved subcarriers (or “tones”) are not used for data transmission. Instead, when a signal has a high PAPR, a compensatory sequence is transmitted on the reserved tones to reduce the PAPR of the signal.
However, the TR approach is associated with PAPR regrowth issues, e.g., the complementary sequence, when added with the original sequence, may reduce the original peak, yet the newly generated peak may be added constructively at nonpeak locations. Therefore, multiple iterations may be required to achieve the desired PAPR level with added complexity. Furthermore, the conventional TR approach is associated with high power on the reserve tones.